DEAR MISS MANNERS:
When does a gentleman offer his arm to a lady as they are walking down the street together?

GENTLE READER:
Strictly speaking, only when he can be practical assisstance to her. That is, when the way is steep, dark, crowded, or puddle-y. However, it is rather a cozy juxtapostion, less comprising than walking hand in hand, and rather enjoyable for people who are fond of each other, so Miss Manners allows some leeway in interpreting what is of practical assisstance. One wouldn't want a lady to feel unloved walking down the street, any more than one would want her to fall of the curb.

Judith Martin